A known data update system performs communication with a navigation device having a large-capacity storage medium such as a hard disk to enable updating of data in the storage medium (see Patent Document 1, for example). The data update system according to Patent Document 1 is structured such that various map data and the like are stored in the storage medium in units of records, and data is updated in such units of records. In other words, for updating in units of records, an updating file having post-update data for the update-targeted record is generated and sent to the navigation device. Then in the navigation device that received the updating file, the data of the update-targeted record stored in the storage medium is overwritten by the data of the received updating file, thereby updating the data of the storage medium. Accordingly, the updating file can be generated as a small-volume file that does not include record data for which updating is not required. Therefore, it is possible to reduce the communication volume, memory volume, and update time needed in order to input the updating file.
[Patent Document 1]    Japanese Patent Application Publication No. JP-A-2004-287705